Conventionally, the majority of the heating and cooling or air conditioning devices operating in room temperature range such as refrigerators, freezers, and air conditioners take advantage of the thermal conductivity of a gas refrigerant like chlorofluorocarbon (CFC) gas and its alternatives. More recently, the problem of ozone depletion caused by the discharge of Freon™ gas, and further, the effects of global warming due to discharge of alternative Freon™ have been realized. Therefore, the development of the air conditioning device is strongly desired, which is clean and innovative with high heat transfer capacity as an alternative to the refrigerator using the gaseous refrigerant and causing the high environmental loads due to use of CFC or its alternatives.
Against this background, air conditioning technology that is attracting attention recently is a magnetic heating and cooling technology. Some of the magnetic material, when the magnitude of the magnetic field applied to the magnetic body is changed, varies its own temperature in response to that change, through so-called magnetocaloric effect. The magnetic conditioning device technology is directed to such technology for transporting heat by using a magnetic material expressing the magneto-caloric effect.
For a refrigerator utilizing the magnetic refrigeration technique, for example, a magnetic refrigerator such as that described in Japanese Patent Application No. JP-A No. 2007-147209 transports heat by using heat conduction of solid material. This magnetic refrigerator causes to conduct heat by the configuration described below.
A positive magnetic member that increases in temperature when applied with magnetism or magnetic field and a negative magnetic member that decreases in temperature when applied with magnetism are alternately arranged at predetermined intervals. A pair of the positive and the negative magnetic members constitute a magnetic member block. A magnetic member unit is formed by arranging a plurality of the magnetic blocks annually. A heat conducting member for selectively inserting into or removing from between the positive and negative magnetic members arranged on the magnetic member unit is disposed between the positive and negative magnetic members. A magnetic circuit is formed by arranging permanent magnets disposed on a hub-shaped rotating member which is concentric with and has substantially the same inner and outer diameters as this magnetic member unit. Further, the rotating member on which permanent magnets are disposed is disposed so as to face the magnetic members and is caused to rotate relative to the magnetic member unit. By this rotation of the rotating member, the positive magnetic member and the negative magnetic member are simultaneously applied with magnetism and the magnetism is then removed. The heat conducting member is selectively inserted into or removed from between the positive and negative magnetic members at predetermined timing in accordance with the rotation of the rotating member. Consequently, the heat generated by the magnetic members through the magnetocaloric effect is transported via the heat conducting member in a direction of the arranged magnetic members. However, in this case, it is necessary to use two different, i.e. positive and negative magnetic members.
In general, the magnitude of the magnetocaloric effect of the positive magnetic member and that of the negative magnetic member are different from each other. Specifically, the magnetocaloric effect of the negative magnetic material is small compared to the magnetocaloric effect of the positive magnetic material. Therefore, in the case of a magnetic refrigerator using a magnetic body of two different, positive and negative members, since it is impossible to obtain a uniform magnetocaloric effect, thus the heat transfer efficiency of the magnetic refrigerator overall is poor. It is possible to increase the heat transfer efficiency when a uniform magnetocaloric effect is obtained. Thus, there is room for improvement in this respect. Further, the material of the negative magnetic material is relatively of rare materials as compared to the material of the positive magnetic material, the magnetic refrigerator becomes more expensive.
Furthermore, since the magnetic circuit applying or removing a magnetic field simultaneously the two, i.e. positive and negative materials is large, a large and heavy magnetic refrigerator is the result. If the weight of the magnetic circuit can be smaller, it is possible to reduce the size of the magnetic refrigerator and to lower the cost and weight. In this regard, there is further room for improvement.